Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Mon Jul 09 2018
Valid 12Z Thu Jul 12 2018 - 12Z Mon Jul 16 2018
...Pattern overview/Guidance evaluation/Preferences with weather
highlights...
Latest models and ensembles this evening show better than average
agreement on the evolution of the synoptic pattern across North
America through the medium range period. A mid- and upper-level
trough lifting out of the Northeast will bring another shot of
cool air into the Northeast late this week while playing a key
role in steering Tropical Cyclone Chris northeastward at some
distance off the New England coast on Thursday. The UKMET
continues to be the outlier by bringing the storm very close to
New England. This scenario is considered to be of low
probability. Consult NHC products for latest information on Chris.
Meanwhile, a subtropical high will anchor itself over the central
Plains late this week as a couple of mid-latitude shortwave
troughs move across western Canada just north of the
U.S.-Canadian border. Models agree that the first shortwave will
bring a cold front across the northern Plains into the Great Lakes
where thunderstorms could become strong Wednesday and Thursday.
Another front is forecast to form in the Pacific Northwest and
then move into the northern Plains in the weekend with scattered
showers and thunderstorms.
From the southeastern U.S. westward along the Gulf Coast, a
dissipating front will keep a good chance of showers and
thunderstorms in the vicinity through the weekend. Monsoonal
moisture will linger across the Four Corners area where locally
heavy downpours will be possible through early next week.
Meanwhile, triple-digit heat is forecast for the interior sections
of the Pacific Northwest into the Intermountain region as well as
interior California through the weekend, as cool air filters into
the northern Plains behind the second cold front.
Given the better than average agreement in the latest guidance,
the latest WPC forecast blend utilized a majority weight of
operational models (18Z GFS and 12Z ECMWF/CMC) versus 18Z
GEFS/ECMWF means through day 5 Fri and then trended toward an even
model/ensemble blend among GFS/ECMWF runs and their means.
Kong
WPC medium range 500 mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indexes are found at:
http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
http://www.wpc.ncep.noaa.gov/heat_index.shtml